6.0.1 The Socket() call

The Socket() call accepts three arguments: family, type, and protocol. It supports the following three combinations of family and type:

1. AF_INET/SOCK_STREAM: this combination specifies that the user wants to create a TCP socket. The following system calls are allowed on a TCP socket: Close(), Bind(), Accept(), Connect(), Write(), Read(), and Setsockopt(). There is no Listen() call, its functionality is subsumed by the Accept() call as described in Section 7

2. AF_INET/SOCK_DGRAM: this combination specifies that the user wants to create a UDP socket. The following system calls are allowed on a UDP socket: Close(), Bind(), Sendto(), Recvfrom(), and Setsockopt().
3. AF_INET/SOCK_ICMP: this combination specifies that the user wants to create an ICMP socket. The following system calls are allowed on an ICMP socket: Close() and Recvfrom().
4. AF_ROUTE/SOCK_RAW: this combination specifies that the user wants to create a routing socket. The following system calls are allowed on a routing socket: Close(), Write(), and Setsockopt().